Alkylene oxide-adducted hydrocarbyl amides have efficacious detergency properties. Their usefulness in hydrocarbon fuels, e.g. fuels in the gasoline or diesel boiling range, is known for preventing deposits in internal combustion engines, controlling octane requirement increases and reducing octane requirement. In addition, the combustion is improved through the use of certain of these compounds. The driveability of vehicles is believed to be enhanced when using fuels containing alkylene oxide-adducted hydrocarbyl amides.
U.S. Pat. No. 4,297,107 to Boehmke, issued on Oct. 27, 1981, discloses a fuel comprising a hydrocarbon, water and an emulsifier wherein the emulsifier is a non-ionic emulsifier and comprises the addition product of ethylene oxide or propylene oxide and a carboxylic acid amide with 9 to 21 carbon atoms.
U.S. Pat. No. 6,312,481 to Lin et al., issued on Nov. 6, 2001, discloses the use of monoamide-containing polyether alcohol compounds as additives in fuel compositions and the use of these compounds to decrease intake valve deposits, control octane requirement increase, and reduce octane requirement.
The preparation of alkylene oxide-adducted hydrocarbyl amides may be carried out by methods familiar to one skilled in the art. For example, one may begin by reacting a fatty acid ester with a mono- or di-hydroxy hydrocarbyl amine to first yield a hydroxylated fatty acid amide as an intermediate reaction product. The alkylene oxide-adducted hydrocarbyl amide can then be obtained by further reaction of the intermediate with an alkylene oxide, such as ethylene oxide or propylene oxide. However, during the course of the reaction, low molecular weight by-products, particularly amine by-products, e.g. alkoxylated amines, such as propoxylated diethanolamines, are produced that are counter beneficial to the desired properties of the alkylene oxide-adducted hydrocarbyl amide when employed as a fuel additive. Such amine by-products are polar, basic and water soluble, resulting in the tendency to accumulate in the water bottoms of fuel storage tanks and on metal surfaces. Fuel tank water bottoms are notorious for harboring numerous accumulated compounds. Under the right conditions, certain low molecular weight amines may react with certain other compounds present, e.g. acidic corrosion inhibitors, possibly forming salts or gums which could potentially form deposits within the distribution system, e.g. filters, flow meters, etc. Within an internal combustion engine, there may be interactions between the amine by-products and other additive components in fuel compositions that could aggravate engine performance due to increased engine wear or sludge or varnish accumulation. Removal of amine by-products resulting from the preparation of alkylene oxide-adducted hydrocarbyl amides is complicated because of the propensity of these materials to form emulsions with aqueous extractions. Thus, it is highly desirable to minimize amine by-products from fuel additive packages containing alkylene oxide-adducted hydrocarbyl amides.
In addition, an important factor in engine no-harm performance is the compatibility of the fuel additive with the engine lubricating oil. Typically, a fraction of most fuel additives survives the combustion process intact and migrates past the piston rings into the crankcase. It is therefore very important that the additive not react negatively with the engine oil in ways that harm the oils functionality, e.g. sediment or cloud formation.
Commonly assigned copending U.S. patent application Ser. No. 10/993,344, filed Nov. 19, 2004, discloses a process for preparing alkylene oxide-adducted hydrocarbyl amides having very low residual levels of amine by-products, particularly alkoxylated amines such as propoxylated diethanolamines (PO-DEA). This process provides reduced levels of amine by-products down to less than 2 wt %.